1. Field of the Invention
The present invention relates to an radiographic apparatus, and more particularly to a portable radiographic apparatus or a radiographic apparatus of a cassette type.
2. Related Background Art
Up to now, an apparatus or a system that irradiates an object with radiation and detects the intensity distribution of the radiation transmitted through the object to obtain a radiation image of the object has been generally widely utilized in the field of industrial non-destructive inspection and medical diagnosis. As a general method such radiography, there is a film/screen method with respect to x-rays. This is a radiographic method that combines a photographic film with a phosphor having a sensitivity with respect to the x-rays. In that method, a sheet-like phosphor made of a rare earth material that emits light upon receiving the x-rays is held in close contact with both surfaces of the photosensitive film, the x-rays transmitted through the object are received by the phosphor and converted into visible light, the visible light is caught by the photosensitive film, and a latent image formed on the film is developed through chemical treatment, whereby an x-ray image (intensity distribution of radiation) can be visualized.
On the other hand, with the progress of the digital technology in recent years, there has been demanded a system in which the radiation image is converted into an electric signal, and after the electric signal is subjected to image processing, the electric signal is reproduced as a visible image on a CRT or the like, thereby to obtain high-quality radiation image information. As a method of converting the radiation image into the electric signal, there has been proposed in Japanese Patent Application Laid-Open No. 55-12429, Japanese Patent Application Laid-Open No. 56-11395, etc., a radiation image recording/reproducing system in which an image of radiation transmitted through an object is stored in a photostimulable phosphor sheet as a latent image once, and thereafter an excitation light such as a laser beam is irradiated onto the phosphor to read the latent image photoelectrically, thereby outputting the radiation image information as a visible image on the basis of the read electric signal. This method is called xe2x80x9ccomputed radiographyxe2x80x9d.
Also, with the progress in the semiconductor process technology in recent years, there has been developed a device for radiographing the radiation image likewise using a semiconductor sensor. Because the system of this type has a very wide dynamic range as compared with a conventional radiographic system using photosensitive film, the system is relatively insensitive to variations in the amount of exposure of radiation, resulting in the advantage that an appropriate radiation image is likely to be obtained. In addition, there is another advantage in that no chemical developing process is required, allowing the instant obtaining of an output image.
FIG. 1 shows a conceptual diagram of a system using a radiographic apparatus, and an x-ray image taking apparatus (a radiographic apparatus) 1 includes an x-ray image detecting sensor 2 therein, and x-rays irradiated from an x-ray generating device 3 and transmitted through an object S are detected by the x-ray image sensor 2 made up of a plurality of photoelectric conversion elements which are arranged in a two-dimensional grating-like fashion. An image processing means 4 subjects an image signal outputted from the x-ray image sensor 2 to digital image processing, and a monitor 5 displays the image signal which has been subjected to the digital image processing as an x-ray image of the object S.
Up to now, radiographic apparatus of that type are located in a radiation room for use, but there has been recently demanded a so-called xe2x80x9celectronic cassettexe2x80x9d or xe2x80x9cdigital cassettexe2x80x9d, which is a radiographic apparatus which is thin, light in weight and portable, because such a cassette permits faseter radiography and of more various body parts.
FIG. 2 is a vertical cross-sectional view of a conventional electronic cassette, in which a casing 11 is fitted with a support 13 through a spacer 12. On the support 13 is disposed an x-ray image detection panel 14 in which a phosphor 14a that converts irradiated x-rays into visible light, a plurality of photoelectric conversion elements 14b arranged in a grating-like fashion which convert the converted visible light into an electric signal, and a substrate 14c that supports the photoelectric conversion elements 14b are laminated one on another. Also, the photoelectric conversion elements 14b are connected to a circuit board 16 disposed on a lower surface of the support 13, on which electronic parts that process an electric signal are mounted, through a flexible circuit board 15 on which are mounted electronic parts that process an electric signal that has been generated by photoelectric conversion.
Radiography using an electronic cassette is different from that using a fixed type radiographic apparatus, for its arrangement with respect to a patient changes depending on the body part to be radiographed. That is, it is desirable that the cassette may be used in such a manner that the patient gets directly on the cassette or holds the cassette in his or her arms. For example, in the case of radiographing extremities of a patient, the cassette is disposed horizontally, the patient lies or stands on the upper surface of the cassette, and the x-rays are irradiated onto the patient from the opposite side. Therefore, unlike the fixed type apparatus, the electronic cassette must be designed with a strength that withstands a load applied by the subject during radiographing.
Also, the operator must handle and manipulate the cassette, and drop the cassette or make the cassette collide with something by mistake. In view of the possibility of such accidents, the structural elements of the cassette (at least an x-ray image sensor inside the cassette) must be protected so that normal functioning is maintained.
Therefore, it is required that the electronic cassette is designed taking strength, vibration resistance, and shock resistance into consideration. For that reason, it is required that a casing that contains the x-ray image detection panel and a support that supports the x-ray image detection panel particularly rigid in structure. This structure prevents the cassette from being small in size or light in weight.
In order to solve the above problem, three has been proposed a structure in which the casing 11 and the spacer 12 are fixed to each other through an elastic body 21 as shown in FIG. 3. However, while that structure exhibits resistance against loads, shocks, vibrations, and the like in the direction in which the x-rays are incident, that is, in a thickness direction of the cassette, it entails a disadvantage due to deformation of the elastic body 21 in a direction substantially orthogonal to the direction of incidence of the x-rays (a direction substantially parallel to the detection plane of the x-ray image detection panel), that is, in a lateral direction of the cassette. Then, for example, in the case where the cassette falls down on the lateral side of the cassette, there is a fear that the flexible circuit board 15 extending around the side of the support 13 may be sandwiched between the support 13 and the casing 11 and be damaged.
The present invention has been made to eliminate or reduce the above-described problems, and therefore an object of the present invention is to provide a thin, light, and portable radiographic apparatus which is capable of reducing shocks to the structural elements of a cassette in a lateral direction, that is, in a direction substantially parallel to the detection surface of the x-ray image detection panel.
According to one aspect of the present invention, there is provided a radiographic apparatus including a radiation detector having a detection plane detecting the radiation image;
a support supporting on a front surface thereof the radiation detector;
a casing housing the radiation detector and the support; and
a shock absorber placed at least any one of on a side wall of the casing, on a side wall of the support, in a side wall of the casing or between the side wall of the casing and the side wall of the support.